The present invention relates to hermetic terminal assemblies and more particularly to an improved seal structure between an electrically conductive terminal pin and the wall of the assembly through which the terminal pin extends from within the assembly to ambient.
It is generally well known in the electrical terminal assembly art to utilize layers of differing materials to seal a terminal pin to a housing. For example, U.S. Pat. No. 4,308,323, issued to Benjamin Bowsky teaches first and second glass materials surrounding and extending coaxially relative each other and a terminal pin which extends from within a battery through the battery wall, the first material being bonded to the pin and the second material being bonded to the first material and the wall, the object of the differing coextensive first and second materials being to provide an overall seal which exhibits a greater resistance to attack by chemicals than by an individual or sole material. More recently issued U.S. Pat. No. 4,514,590, issued to James C. Kyle on Apr. 30, 1985 employs terminal pin sealing layers of different materials, each of which generally extends in planar, sandwich form with the others normal to the longitudinal axis of the pin between the pin and the housing, the layers of different materials having different coefficients of thermal expansion to compensate for stresses in the terminal assembly as a result of temperature changes.
The present invention, unlike the prior art, recognizes that different electrochemical conditions exist within and outside a hermetically sealed assembly, then solves this recognized problem in sealing terminal pins in hermetically sealed assemblies in a unique and novel manner, requiring a minimum of materials and processing steps in both straight-forward and efficient manufacture and assembly steps and, at the same time, assuring a long lasting terminal pin seal both internally and externally of the hermetic assembly. The structure of the present invention accomplishes this without sacrifice of chemical integrity and stability of the seal, providing a terminal pin seal structure resistant to recognized differing conditions of humidity and corrosion without undesirable bubbles and pockets therein and with controlled seal stress conditions, utilizing these controlled stress conditions for a more efficient and effective seal through regulated material viscosity and compression characteristics. The structure of the present invention lends itself readily for use with hermetic terminal assemblies such as lithium batteries particularly, when constructed in accordance with the end closure structural arrangement as set forth in the aforementioned parent application, of which this application is a continuation-in-part.
Various other features of the present invention will become obvious to one skilled in the art upon reading the disclosure set forth herein. Although not to be considered in any manner as limited thereto, the unique structural features of the present invention have particular utility in the battery art--especially in batteries of the lithium type.